ENHANCED DATA RATES FOR GLOBAL EVOLUTION

A SYNOPSIS

ON

(Title of the Seminar)

BY

(Name of the Students in the Group)

Under the guidance of

Internal Guide External Guide(Optional)

(ABCD) ( XYZ )

Department of Computer Engineering

Rajiv Gandhi Institute of Technology
Juhu-Versova Link Road Versova, Andheri (w), Mumbai-53

University of Mumbai

April - 2011

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

1
Department of Computer Engineering
Rajiv Gandhi Institute of Technology
Juhu-Versova Link Road, Versova, Andheri(West) Mumbai -53

CERTIFICATE
This is to certify that

1. Ansari Shaiwaz (677)

2. Ansari Shabnam (672)
3. Mujwar Sana (676)

Have satisfactory completed the seminar entitled

(Enhanced Data Rates For Gsm Evolution)

Towards the partial fulfillment of the

BACHELOR OF ENGINEERING
IN
(COMPUTER ENGINEERING)

as laid by University of Mumbai.

Guide H.O.D.
(Prof. Name) (Prof. S. B. Wankhade)

Principal
(Dr. Udhav Bhosle)

Internal Examiner External Examiner

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

CONTENTS

1. ABSTRACT:
2. INTRODUCTION:
2.1 High Speed Wireless Terms:-
2.2 Advantage of EDGE over GSM
2.3 Types of EDGE:-
3. REVIEW OF LITERATURE
4. EXISTING SYSTEM:
4.1 GSM (Global System for Mobile Communication):
4.2 GPRS (General Packet Radio Service):
4.3 EDGE (Enhanced Data rates for Global Evolution):
4.4 The Second Generation Evolution to EDGE:-
4.5 Offered EDGE Bearer Services:-
5. Existing System Architecture
5.1 The Technology behind EDGE:-
5.2 EDGE in GSM Systems:
5.3 Effects on the GSM System Architecture:
6. Development Tools:-
7. Future Scope
8. Conclusion
9. References

EDGE
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1. ABSTRACT:
This paper gives an overview of the EDGE concept. It gives a global overview of second
generation systems migration to International Mobile Telecommunications in the year 2000
(IMT-2000). It also gives the rationale behind the development of the EDGE concept, including
standardization background and efforts, aspects of introducing EDGE in GSM, and capacity and
coverage performance.

2. INTRODUCTION:

In line with the efforts of International Telecommunication Union (ITU) to provide global
recommendations for IMT-2000, spectrum identification has been made, identifying parts of the
2 GHz band for IMT-2000 usage. Deploying IMT-2000 capable systems is however not limited
to this spectrum band. The EDGE concept, a new TDMA-based radio access technology for both
TDMA/136 and Global System for Mobile Communications (GSM) systems, provides third-
generation capabilities in the existing 800, 900, 1800, and 1900 MHz) frequency bands.
Enhanced Data rates for Global Evolution (EDGE) are a radio based high-speed mobile data
standards. A technology that gives Global System for Mobile Communications (GSM) the
capacity to handle services for the third generation of mobile network. EDGE was initially
developed for mobile network operators who fail to win Universal Mobile Telephone System
(UMTS) spectrum. EDGE gives incumbent GSM operators the opportunity to offer data services
at speeds that are near to those available on UMTS networks.
EDGE enables services like multimedia emailing, Web infotainment and video conferencing to
be easily accessible from wireless terminals.

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION
2. 1 High Speed Wireless Terms:-

2.1.1 :- 1G or first generation:

The first generation of cellular networks used analog transmission. This is available in all
cellular markets today.

2.1.2 :- 2G or second generation:

The second generation of wireless networks uses digital transmission for voice signals. The
development of digital transmission allowed carriers to fit more calls on the same frequency and
eliminate more noise and static on each call. Digital technology also improved the battery life for
wireless phones and added many vertical features like Caller ID, text messaging and intelligent
roaming. In this network, data is usually transported over voice channels at speeds ranging from
9.6 kbps to 14.4 kbps.

2.1.3 :- 2.5G or 2.5 generation:

2.5G doesn't change how voice is transported, but introduced packet data services, allowing for
speeds of 20 to 40 kbps about the same speed as a dial-up service.

2.1.4:- 3G or third generation:

The third generation of wireless networks increases the speed of packet data transport through
the network to speeds above 100 kbps.

EDGE
ENHANCED DATA RATES FOR GLOBAL EVOLUTION

802.11

FIG 1.1

EDGE
ENHANCED DATA RATES FOR GLOBAL EVOLUTION
6

FIG 1.2

EDGE
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2.2 Advantage of EDGE over GSM

In the mid-1990s, GSM deployment gathered pace around the world, and this growth
continues today. More than 80 percent of all mobile users in the world are served by GSM, and
every month approximately 40 million new users join the GSM community. As a mobile
technology, GSM has unmatched coverage, economies of scale, simplicity and maturity, and
these are all benefi ts that EDGE hares too.

The common view from the GSM/WCDMA operators is that GSM will be used beyond2020,
meaning that GSM and EDGE will provide the fundamental coverage for voice and data for
many years to come. Standardized in 3GPP as part of the GSM/WCDMA family, EDGE is a
simple and costeffective upgrade that provides a more than three-fold increase in both the
capacity and performance of GSM/GPRS networks.oes this by methods of coding and
Transmitting data,delivering higher bit rates per radio channel,as illustrated in Figure 1.

Introducing EDGE normally only requires asoftware upgrade of the existing GSM/GPRS
network. It does not require any new sites or new spectrum, and has no impact on existing cell or
frequency plans.With EDGE, GSM operators can extend their
service offering to include high-performance mobile data. They can rapidly target all
potential data users thanks to EDGE’s ability to achieve high geographic and population
coverage in a short period of time. This is one of the main reasons that several hundred GSM
networks have already upgraded to EDGE.EDGE is not launched as a service; it is an enabler of
new services and faster internet access – an almost mandatory upgrade, with a clear and
compelling business case.

EDGE
ENHANCED DATA RATES FOR GLOBAL EVOLUTION

Fig 1.3

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

Today’s EDGE technology offers greatly improved performance compared with

standard GPRS and the fi rst implementations of EDGE. The increased user bit-rates and reduced
latency offered by EDGE enhance existing applications and make new services – like music
downloads, mobile broadband and messaging services – more attractive.
The performance of EDGE, as experienced by the end-user, is dependent on a variety of system
characteristics. For example, a web download consists of multiple requests and
downloads of objects and, consequently, the time it takes to download a page depends
on the end-to-end round-trip time and user bit-rates in the system – which are the main
performance indicators for any packet data system. Performance is normally evaluated across a
common set of subscriber applications. Today’s state-of-the-art EDGE networks typically offer
user speeds of 200kbps, with end-to-end round-trip time (latency) of 150ms (as shown in Figure
7). Features like advanced link quality control and persistent scheduling have improved
performance significantly over standard GPRS and the first implementations
of EDGE. For example, the time it takes to download a web page is about one-quarter of
that taken with standard GPRS.Network effi ciency also impacts end-user performance.
Compared with basic implementations, the latest EDGE systems have greatly improved resource
utilization, multiplexing capabilities for several users and other capabilities that maximize
network effi ciency

FIG 1.4
10
2.2 Types of EDGE:-

EDGE
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2.2.1 EDGE Classic:

The EDGE Classic air-interface is based on the EDGE standard developed by the European
Telecommunications Standards Institute (ETSI). EDGE Classic is ETSI-EDGE with minor
modifications, primarily information related to ANSI-136, that enables it to be overlaid as a
packet data carrier on top of the existing ANSI-136 30 kHz air-interface. Examples of such
information are pointers to the ANSI-136 Digital Control Channels (DCCH) covered by the
EDGE cell and some of the broadcast information available on the ANSI-136 DCCH.

A class B ANSI-136 terminal (a terminal with ANSI-136 voice and EDGE packet data) needs
this information when camping on the EDGE packet data channel in order to originate and
terminate circuit-switched services, e.g., incoming and outgoing voice calls.
Operators who can set aside 2.4 MHz of initial spectrum for data applications can overlay

2.2.2 EDGE COMPACT

EDGE Compact uses the same modulation scheme as EDGE Classic. However, there are certain
key differences that enable it to be deployed in less than 1 MHz of spectrum. The key
characteristics that differentiate EDGE Compact from EDGE Classic are:

2.2.2.1 Inter base station time synchronization:

A key characteristic of EDGE Compact is that the base stations are time synchronized with each
other. This makes it possible to allocate common control channels in such a way as to prevent
simultaneous transmission and reception. This creates a higher effective reuse, necessary for
control signaling, e.g., 3/9 or 4/12. The base station synchronization is carried out such that the
timeslot structure is aligned between sectors and the hyper-frame structures are aligned between
all sectors.

11

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2.2.2.2 Time Groups and Discontinuous transmission:

Each base station site is typically allocated at least three frequencies, one per sector, using a 1/3
frequency re-use pattern. Inter base station time synchronization makes
it possible to create time-groups within every frequency. Each sector is assigned one time-group.
EDGE Compact is capable of supporting up to four time-groups per carrier. The typical re-use
configurations with three carriers are:

* 3/9 re-use using three out of the four time-groups

*4/12 re-uses using all four time-groups.

When a sector belonging to one of the time-groups transmits or receives common control
signaling, the sectors belonging to other time-groups are idle, i.e., are silent
in both uplink and downlink. It is worth noting that the data traffic is carried over these same
frequencies without using the time group concept. This results in a
1/3 re-use pattern for data traffic.

 New logical control channel combination based on a standard 52 multi-frame

 Time Group rotation of Control Channel.

12

EDGE
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3. REVIEW OF LITERATURE

Since its standardization was finalized by the 3GPP in 2000, EDGE – Enhanced Data rates for
Global Evolution – has achieved market maturity in terms of networks, terminals and business
models. Upgrading to EDGE has become a natural step for operators who want to offer high-
performance mobile data services over GSM. EDGE gives them a costeffective way to reach the
mass market and boost the uptake of mobile data services. The common view from
GSM/WCDMA operatorsis that GSM will be used beyond 2020,providing nationwide coverage
for voice and data for many years to come.EDGE combines effi cient technology, a simple
upgrade path and support for many GSM and WCDMA terminals to create a compelling
business case.
Three-quarters of all GSM and UMTS terminals sold now support EDGE, from
low to high-end. EDGE is a viable alternative for providing fast internet access in markets where
fi xed network infrastructure is yet to be established.

The performance of EDGE has improved steadily since its introduction: today it offers
user bit rates up to 250kbps, with end-to-end latency of less than 150ms. This performance is
suffi cient to make any data service available today attractive to users.
EDGE is an important complement to mobile broadband services presently
delivered over WCDMA/HSPA and in future LTE networks. EDGE provides both a fast
way to achieve good indoor and outdoor coverage, and to meet increasing demand for
mobile internet services through optimal use of available radio spectrum.
To build on the global success of EDGE,the GSM community has standardized EDGE
Evolution, which further improves performance and capacity. EDGE Evolution
more than doubles end-user bit rates and reduces latency signifi cantly. What is more, all this can
be done using existing infrastructure, protecting current GSM and EDGEinvestments for many
years to come.

13

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

4. EXISTING SYSTEM:

4.1 GSM (Global System for Mobile Communication):

The largest digital mobile standard in use today, used in over 170 countries worldwide. More
than 70 percent of the world's digital phones operate on GSM technology. Implemented in
400MHz, 800MHz, 900MHz, 1800MHz and 1900MHz frequency bands.

4.2 GPRS (General Packet Radio Service):

An enhancement for GSM core networks that introduces packet data transmission, GPRS uses
radio spectrum very efficiently and provides users with "always on"? connectivity and greater
bandwidth. GPRS users will eventually enjoy worldwide roaming while 1xRTT users today
cannot. GPRS is the internationally accepted standard for roaming based on GSM technology,
which is employed by over 170 countries around the world.

4.3 EDGE (Enhanced Data rates for Global Evolution):

EDGE is a technology that gives GSM Networks the capacity to handle services for 3G. EDGE
was developed to enable the transmission of large amounts of data at peak rates of up to
472kbps. Users should experience average speeds of 80 kbps to 130 kbps. EDGE deployment
will begin in 2003 with full deployment finishing in 2004. EDGE devices are backwards
compatible with GPRS and will be able to operate on GPRS networks where EDGE has not yet
been deployed.

Performance in a live network has been measured in order to ensure that EDGE Evolution
provides benefits in real situations. Quality measurements have been collected in a number of
typical cells in operators’ networks and the results show that EDGE Evolution will signifi cantly
improve bit rates in the whole cell. Figure 7 shows the cumulative distribution of the time slot bit
rate in an urban cell with medium
quality. EDGE Evolution increases the average bit rate by 86 percent (from 42 to 78kbps)
compared with EDGE.
olution

14

EDGE
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4.3.1 Enhanced application performance over EDGE

EDGE enhances services provided by GSM systems with higher user bit rates and
multimedia capabilities. EDGE is also an evolutionary path towards providing thirdgeneration
services. The perceived end-user performance enabled by EDGE is good enough to make any
service available today more attractive (Table 1).
This includes e-mail, web browsing, music downloads and mobile TV.

15

EDGE
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4.4 Implementing EDGE Evolution

The installed base of GSM/EDGE equipment is very large, so great care has been taken to ensure
that the impact of EDGE Evolution on base station hardware is minimized. The different
enhancements may be gradually – and to some extent independently – introduced in the network,
most of them as software
upgrades. Current network architecture remains unchanged. Handsets will require more
extensive modifi cations, but are replaced at a much higher rate. A large number of handset
vendors are foreseen to adhere to EDGE Evolution, and handsets with increasing levels of EDGE
Evolution functionality are expected to beavailable from 2010.Figures 5 and 6 show examples of
the increased peak bit rates and spectrum effi ciency provided by GPRS, EDGE and different
stages of EDGE Evolution implementation.

16

EDGE
ENHANCED DATA RATES FOR GLOBAL EVOLUTION

FIG 4.1

17

EDGE
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4.4 The Second Generation Evolution to EDGE:-

GSM and TDMA/136 are two second-generation cellular standards with worldwide success.
Today GSM is used by more than 135 million subscribers in over 100 countries, and the
TDMA/136 system family (including EIA-553 and IS-54) serves over 95 million subscribers in
over 100 countries worldwide. Although speech is still the main service in these systems, support
for data communication over the radio interface is being rapidly improved. The current GSM
standard provides data services with user bit rates up to 14.4 kb/s for circuit switched data and up
to 22.8 kb/s for packet data. Higher bit rates can be achieved with multislot operation, but since
both high-speed circuit-switched data (HSCSD) and General Packet Radio Service (GPRS) are
based on the original Gaussian minimum shift keying (GMSK) modulation, the increase of bit
rates is slight.

Figure.4.2

18

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

EDGE uses high-level modulation in 200 kHz TDMA and is based on plug-in transceiver
equipment. Universal Mobile Telecommunications Service (UMTS) is a new radio access
network based on 5 MHz wideband code division multiple access (WCDMA). UMTS can be
used in both new and existing spectra.
By adding third-generation capabilities to the GSM network implies the addition of packet
switching, Internet access, and IP connectivity capabilities. With this approach, the existing
mobile networks will reuse the elements of mobility support, user authentication/service
handling, and circuit switching. Packet switching/IP capabilities are added to provide a mobile
multimedia core network by evolving existing mobile telephony networks.

4.5 Offered EDGE Bearer Services:-

The result of the EDGE radio interface and protocol enhancements is a set of bearers that are
offered from the network to carry data over the wireless link. The definition of these bearers
specifies what the user can expect from EDGE.

4.5.1 Packet-Switched Bearers:

The GPRS architecture provides IP connectivity from the mobile station to an external fixed IP
network. For each bearer that serves a connection, a quality of service (QoS) profile is defined.
The parameters included are priority, reliability, delay, and maximum and mean bit rate. A
specified combination of these parameters defines a bearer, and different such bearers can be
selected to suit the needs of different applications.
EDGE introduction calls for an updated parameter space for QoS parameters. For example, the
maximum bit rate possible for an EGPRS bearer will be at least 384 kb/s for terminal speeds up
to 100 km/h and 144 kb/s for terminal speeds up to 250 km/hr [13]. Also, mean bit rate and delay
classes may be affected by the introduction of EDGE.

19

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION
4.5.2 Circuit-Switched Bearers:

The current GSM standard supports both transparent and non transparent bearers. Eight
transparent bearers are defined, offering constant bit rates in the range of 9.6–64 kb/s. A
nontransparent bearer employs a radio link protocol (RLP) to ensure virtually error-free data
delivery. For this case, there are eight bearers offering maximum user bit rates ranging from 4.8
to 57.6 kb/s. The actual user bit rate may vary according to the channel quality and the resulting
rate of retransmission.
The introduction of EDGE implies no change of bearer definitions. The bit rates are the same,
but what is new is the way the bearers are realized in terms of the channel coding schemes
defined in Table 2. For example, a 57.6 kb/s nontransparent bearer can be realized with coding
scheme ECSD TCS-1 and two time slots, while the same bearer requires four time slots with
standard GSM (using coding scheme TCH/F14.4). Thus, EDGE circuit-switched transmission
makes the high bit rate bearers available with fewer time slots, which is advantageous from a
terminal implementation perspective. Additionally, since each user needs fewer time slots, more
users can be accepted, which increases the capacity of the system.

4.5.3 Asymmetric Services Due to Terminal Implementation:

For mobile stations, there is a trade-off between the new possibilities of EDGE and the
requirements for low cost, small size, and long battery life. The 8-PSK transmitter is more of a
challenge to incorporate into a low-complexity mobile station with today’s commercial
technology than is the receiver. The approach taken by ETSI is to standardize two mobile
classes, one that requires only GMSK transmission in the uplink and 8-PSK in the downlink, and
one that requires 8- PSK in both links.
For the former class, the uplink bit rate will be limited to that of GSM/GPRS, while the EDGE
bit rate is still provided in the downlink. Since most services are expected to require higher bit
rates in the downlink than in the uplink, this is a way of providing attractive services with a low
complexity mobile station. Similarly, the number of time slots available in up- and downlinks
need not be the same. Transparent services will, however, be symmetrical. This is not a new
evolution path for GSM mobiles: the GSM standard already includes a large number of mobile
station classes, ranging from single-slot mobile stations with low complexity to eight-slot
mobiles providing high bit rates. EDGE will introduce a number of new classes, with different
combinations of modulation and multislot capabilities.

20

EDGE
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5.EXISTING SYSTEM ARCHITECTURE

Implementation of EDGE by network operators has been designed to be simple. Only one EDGE
transceiver unit will need to be added to each cell. With most vendors, it is envisaged that
software upgrades to the Base Station Controller (BSCs) and Base Stations can be carried out
remotely. The new EDGE capable transceiver can also handle standard GSM traffic and will
automatically switch to EDGE mode when needed. Some EDGE capable terminals are expected
to support high data rates in the downlink receiver only (i.e. high dates rates can be received but
not sent), whilst others will access EDGE in both uplink and downlinks (i.e. high data rates can
be received and sent).
The later device types will therefore need greater terminal modifications to both the receiver and
the transmitter parts. EDGE is designed for migration into existing GSM and TDMA networks,
enabling operators to offer multimedia and other IP-based services at speeds of up to 384 kbits/s
(possibly 473 kbits/s in the future) in wide area networks.
An important attraction of EDGE is the smooth evolution and upgrade of existing network
hardware and software, which can be introduced into an operator's current GSM or TDMA
network in existing frequency bands.
In addition, the TDMA industry association, the Universal Wireless Communications
Corporation, has introduced what it calls EDGE Compact.

5.1 The Technology behind EDGE:-

The first stepping stone in migration path to third generation wireless mobile services (3G) is the
General Packet Radio Services, GPRS, a packet-switched technology that delivers speeds of up
to 115kbps. If GPRS is already in place, Enhanced Data rates for Global Evolution (EDGE)
technology is most effective as the second stepping stone that gives a low impact migration.
Only software upgrades and EDGE plug-in transceiver units are needed. The approach protects
operators' investments by allowing them to reuse their existing network equipment and radio
systems.
EDGE provides an evolutionary migration path from GPRS to UMTS by implementing the
changes in modulation for implementing UMTS later. The idea behind EDGE is to eke out even
higher data rates on the current 200 kHz GSM radio carrier by changing the type of modulation
used, whilst still working with current circuit (and packet) switches.
EDGE is primarily a radio interface improvement, but in a more general context it can also be
viewed as a system concept that allows the GSM and TDMA/136 networks to offer a set of new
services.

21

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION
5.1.1 Improvement in Existing Radio Interface Network:

One fundamental characteristic of a cellular system is that different users tend to have different
channel qualities in terms of signal-to-interference ratio (SIR), due to differences in distance to
the base station, fading, and interference. Despite attempts to affect channel quality through
power control, there will typically be a distribution of channel quality in a system, for example,
according to the left side of Figure 4. A traditional service such as speech requires a certain
target SIR to give good quality, below the target the quality is unacceptable, while above the
target the quality is good and practically independent of channel quality.
Thus, the radio network planning must make sure that only a small fraction of users are below
the SIR target. Unfortunately, a large part of the user population will then experience
unnecessarily high SIR (i.e., excellent channel quality from which they cannot benefit). This is
the case for today’s GSM and TDMA/136 systems, for speech and data services, thereby leaving
room for enhancements in spectral efficiency. EDGE is designed to improve the situation by
employing what is referred to here as link quality control.

FIG 5.1

22

EDGE
ENHANCED DATA RATES FOR GLOBAL EVOLUTION
Link quality control adapts the protection of the data to the channel quality so that for all
channel qualities an optimal bit rate is obtained. The principle is illustrated on the right of
Figure 4, showing user quality in terms of information bit rate with EDGE (EGPRS) and
standard GPRS as a function of channel quality. Standard GPRS saturates at rather low
SIR, whereas EDGE user quality increases with increased channel quality. Naturally, to
obtain the characteristics in Figure 4, EDGE must include transmission modes with
significantly higher information bit rates than those of standard GSM and TDMA/136.
This is the reason for the introduction of the new modulation, 8-PSK, which is the core of
the EDGE concept.

5.2.2 Basics of Radio Interface:

The EDGE air interface is intended to facilitate higher rates than those currently
achievable in existing cellular systems. In order to increase the gross bit rate, 8-PSK, a
linear high-level modulation, is introduced. 8-PSK, as shown in Figure 5, is selected
since it provides high data rates, high spectral efficiency, and moderate implementation
complexity. GMSK modulation for GSM is also part of the EDGE system concept.
The symbol rate is 271 kb/s for both modulations, leading to gross bit rates per time slot
of 22.8 kb/s and 69.2 kb/s for GMSK and 8-PSK, respectively (including two stealing bits
per burst). The 8-PSK pulse shape is linearized GMSK, allowing 8PSK to fit into the GSM
spectrum mask.

23

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

FIG 5.2

Many EDGE physical layer parameters are identical those of GSM. The carrier spacing is 200
kHz, and GSM’s TDMA frame structure is unchanged. Also, the 8-PSK burst format is similar: a
burst includes a training sequence of 26 symbols in the middle, three tail symbols at either end,
and 8.25 guard symbols at one end. Each burst carries 2 x 58 data symbols, each comprising 3
bits (Figure. 6). Channel coding and interleaving are intimately related to the layer 2 protocols.

FIG 5.3

24

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION
5.2.3Protocol design:

FIG 5.4

The radio protocol strategy for EDGE is to reuse the protocols of GSM/GPRS whenever
possible, thus minimizing the need for new protocol implementation. However, due to the higher
bit rates and new insights Obtained in the radio protocol field, some protocols are changed to
optimize performance. The EDGE concept includes one packet-switched mode and one circuit-
switched mode, EGPRS and ECSD, respectively.

25

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION
5.2.3.1 Packet-Switched Transmission: EGPRS:-

Due to the higher bit rate and the need to adapt the data protection to the channel quality, the
EDGE radio link control (RLC) protocol is somewhat different from the corresponding GPRS
protocol. The main changes are related to improvements in the link quality control scheme. As
mentioned earlier, link quality control is a common term for techniques to adapt the robustness
of the radio link to varying channel quality. Examples of link quality control techniques are link
adaptation and incremental redundancy.

A link adaptation scheme regularly estimates the link quality and subsequently selects the most
appropriate modulation and coding scheme for coming transmissions in order to maximize the
user bit rate. Another way to cope with link quality variations is incremental redundancy. In an
incremental redundancy scheme, information is first sent with very little coding, yielding a high
bit rate if decoding is immediately successful. If decoding fails, additional coded bits
(redundancy) are sent until decoding succeeds. The more coding that has to be sent, the lower the
resulting bit rate and the higher the delay.

EGPRS supports a combined link adaptation and incremental redundancy scheme. In this
scheme, the initial code rate for the incremental redundancy scheme is based on measurements of
the link quality. Benefits of this approach are the robustness and high throughput of the
incremental redundancy operation in combination with the lower delays and lower memory
requirements enabled by the adaptive initial code rate.

As in GPRS, the different initial code rates are obtained by puncturing a different number of bits
from a common convolution code (rate 1/3). The resulting coding schemes are listed in Table 1.
Incremental redundancy operation is enabled by puncturing a different set of bits each time a
block is retransmitted, whereby the code rate is gradually decreased toward 1/3 for every new
transmission of the block. The selection of the initial modulation and code rate to use is based on
regular measurements of link quality.

26

EDGE
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FIG 5.5

27

EDGE
ENHANCED DATA RATES FOR GLOBAL EVOLUTION

5.2.3.2 Circuit-Switched Transmission: Enhanced CSD:-

For the ECSD mode of EDGE, the aim is to keep the existing GSM circuit-switched
data protocols as intact as possible. A data frame is interleaved over 22 TDMA
frames as in GSM, and three new 8-PSK channel coding schemes are defined along
with the four already existing for GSM. As shown in Table 2, the radio interface rate
varies between 3.6 and 38.8 kb/s per time slot. For nontransparent transmission, the
current assumption is that the radio link protocol of GSM is to be used.

FIG 5.6

28

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

5.3 EDGE in GSM Systems:

Effects on the GSM System Architecture:

The increased bit rates of EDGE put requirements on the GSM/GPRS network architecture.
Figure. 7 illustrates the GSM/GPRS architecture, the shaded parts of which are discussed in this
section. Other nodes and interfaces are not affected at all by EDGE introduction.

FIG 5.7
29

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

An apparent bottleneck is the A-bis interface, which today supports up to 16 kb/s per traffic
channel. With EDGE, the bit rate per traffic channel will approach 64 kb/s, which makes
allocation of multiple A-bis slots to one traffic channel necessary. Alternative asynchronous
transfer mode (ATM) or IP-based solutions to this problem can also be discusses. One important
fact is, however, that the 16 kb/s limit will be exceeded already by the introduction of two coding
schemes (CS3 and CS4) in GPRS, which have a maximal bit rate per traffic channel of 22.8 kb/s.
Consequently, the A-bis limitation problem is being solved outside the EDGE standardization,
and it is therefore a GPRS related, not EDGE-related, modification. For GPRS-based packet data
services, other nodes and interfaces are already capable of handling higher bit rates, and are thus
not affected. For circuit-switched services, the A interface can handle 64 kb/s per user, which is
not exceeded by EDGE circuit-switched bearers.

5.3.2 Impact on GSM Radio Network Planning:

An important prerequisite, which to a large extent will determine the success of EDGE in GSM,
is that a network operator be able to introduce EDGE gradually. For initial deployment, EDGE-
capable transceivers will supplement standard GSM/GPRS transceivers in a subset of the
existing cells where EDGE coverage is desired. Hence, an integrated mix of GSM, GPRS, and
EDGE users will coexist in the same frequency band. To minimize effort and cost for the
network operator, radio network planning (including cell planning, frequency setting of power
and other cell parameters) must not require extensive modification.

5.3.2.1 Coverage Planning :

One characteristic of non-transparent radio link protocols that include automatic repeat request
(ARQ), is that low radio link quality only results in a lower bit rate for the user. Hence, low SIR for a
user does not result in a dropped call, as for speech, but in a temporary decrease of user bit rate.
For transparent bearers, which typically offer a constant bit rate, link quality control must be
extended to incorporate resource allocation, in the sense that the number of dynamically allocated
time slots fits the bit rate and bit error rate (BER) retirements. Transparent bearers, will thus be
available in the entire GSM cell, but require fewer time slots in the center of the cell (where 8-PSK
coding schemes can be used)

30

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

5.3.2.2 Frequency Planning:

Most mature GSM networks of today have an average frequency reuse factor of around 9
(meaning that available frequencies are divided into nine frequency groups). However, there is
also a trend toward tighter reuse factors. With the use of frequency hopping, multiple reuse
patterns (MRP), and discontinuous transmission (DTX), reuse factors as low as 3 become
feasible. EDGE supports a variety of reuse patterns. In fact, by its use of link quality control,
EDGE can be introduced in an arbitrary frequency plan, and benefit from high SIR closer to the
base stations.
EDGE can be introduced in an existing GSM frequency plan, and that it also supports future
high-capacity solutions based on tighter frequency reuse.

5.3.2.3. Channel Management:

In EDGE, a cell typically includes two types of transceivers: standard GSM and EDGE
transceivers (Figure. 8). Each physical channel (time slot) used for traffic in the cell can be
viewed as being one of at least four channel type

􀂾GSM speech and GSM circuit-switched data (CSD)

􀂾GSM packet data (GPRS)

􀂾GSM speech and circuit-switched data (CSD and ECSD)

􀂾Packet data (GPRS and EGPRS)

31

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

FIG 5.8

While standard GSM transceivers support only the first two channel types, EDGE transceivers
support all four. Physical channels are dynamically defined according to the need in the cell. For
example, if a large number of speech users are currently active, the number of channels of the
first and third types is increased, at the expense of fewer GPRS and EGPRS channels.

32

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

6. Development Tools:-

EDGE was first proposed to European Telecommunications Standards Institute (ETSI) in

Europe, as an evolution of GSM at the beginning of 1997. Although EDGE reuses the GSM
carrier bandwidth and time slot structure, it is by no means restricted to use within GSM cellular
systems. Instead, it can be seen as a generic air interface for efficiently providing high bit rates,
facilitating an evolution of existing cellular systems toward third-generation capabilities. After
evaluating a number of different proposals, EDGE was adopted by UWCC in January 1998 as
the outdoor component of 136HS to provide 384 kb/s data services. This was in support of the
technology evolution for GSM and TDMA/ 136 systems.

Since then, EDGE development has been concurrently carried out in ETSI and UWCC to
guarantee a high degree of synergy with both GSM and TDMA/136. The standardization
roadmap for EDGE foresees two phases. In the first phase the emphasis has been placed on
Enhanced GPRS (EGPRS) and Enhanced Circuit-Switched Data (ECSD).
EDGE uses the same TDMA (Time Division Multiple Access) frame structure, logic channel and
200 kHz carrier bandwidth as today's GSM networks, which allows existing cell plans to remain
intact. Its high data transmission speed offers more diverse and media rich content and
applications to GSM subscribers.

33

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

7. FUTURE SCOPE

To improve service performance in general, and facilitate conversational multimedia services,

anumber of enhancements to EDGE have been standardized by the 3GPP. Known collectivelyas
EDGE Evolution, these were included in Release 7 of the 3GPP standard. Peak bit rates of up to
1Mbps and typical bit rates of 400kbps can be expected. Round-trip times will be less than 80ms
and spectrum effi ciency will be more than twice as good as today. EDGE Evolution can be
gradually introduced as software upgrades, taking advantage of the installed base. With EDGE
Evolution, end users will be able to experience mobile internet connections corresponding to a
500kbps ADSL service.EDGE Evolution will improve service performance and enable more effi
cient radio bearers. Different services may have varying performance requirements in different
areas,but EDGE Evolution is expected to improve the perceived performance across all services
by:

✒ Reducing latency to improve the user experience of interactive services and also
to enhance support for conversational services such as multimedia telephony.

✒ Increasing peak and mean bit rates, to improve best-effort services such as web
browsing or music downloads.

✒ Improving spectrum effi ciency, which will particularly benefi t operators in urban
areas where existing frequency spectrum is used to its maximum extent – traffi c
volume can be increased without compromising service performance or
degrading perceived user quality.

✒ Boosting service coverage, for example by reducing interference or allowing more

robust services. Increased terminal sensitivity improves coverage in the noiselimited
scenario.

34

8. CONCLUSION

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

With the continuous globalization of telecommunication standards, the convergence of

TDMA/136 and GSM is a logical next step. The common access of data services for TDMA/136
and GSM can be offered to over 230 million subscribers of both standards, and will thereby
create huge market potential. Due to the convergence of the systems, roaming between both
communities will be possible. Furthermore, the smooth introduction of EDGE in TDMA/136 and
GSM will allow operators to improve services and capacity on demand. Regarding performance,
the presented packet data simulation results show that compared to standard GSM, EDGE
enables significantly higher peak rates, and approximately triples the spectral efficiency. Also,
the packet bit rate coverage of the EDGE concept is improved compared to standard GSM,
enabling existing sites to be reused

ADVANTAGES

 Balanced improved bit rate at all radio conditions

 No hardware, software change to GSM core networks

 Supports download various file types

 Handle four times the traffic of standard GPRS

 Smart & adaptive antennas

 Triples gross data rate by GSM

 Circuit-switched and packet-switched traffic coexist

 Rapid Internet and WAP access

 Service available for EDGE phones without tariff charge

 Avoids creating new system

35

9. References:

EDGE
 ENHANCED DATA RATES FOR GLOBAL EVOLUTION

[1] ETSI TS 03 64 V5.1.0 (1997-11), “Digital Cellular Telecommunications system (Phase 2+);
General Packet Radio Service (GPRS); Overall Description of the GPRS Radio Interface;
Stage 2
(GSM 03.64, v. 5.1.0)

[2] ETSI. GSM 02.60, “General Packet Radio Service (GPRS); Service description; stage 1,” v.
7.0.0, Apr. 1998.

[3] H. Nakamura, H. Tsuboya, M. Nakano, and A. Nakajima, “Applying ATM to Mobile

Infrastructure Networks,” IEEE Commun. Mag., vol. 36, no. 1, Jan. 1998.

[4] K. Zangi, A. Furuskar, and M. Hook, “EDGE: Enhanced Data Rates for Global Evolution of
GSM and IS-136,” Proc. Multi Dimensional Mobile Commun. 1998.

[5] www.siemens.com/mobile

[6] www.ericsson.com/technology/EDGE.shtml

[7] www.mobilegprs.com/edge.htm

[8] www.nuntius.com/solutions24.html

[9] www.business2.com/webguide/0,1660,36843,00.html

[10] www.umtsworld.com/technology/edge.htm

[11] www.privateline.com/Cellbasics/Nokiaedge_wp.pdf

[12] www.siemens.ie/mobile/technologies/edge.htm

[13] www.mtconsultancy.nl/eng/edge_E.htm

[14] www.3g-generation.com/gprs_and_edge.htm

[15] www.opencae.cz/hw/hw_standard_gsm.html

[16] www.wikipedia.org/wiki/EDGE.

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EDGE